Mutual neutralization of C$_{60}^+$ and C$_{60}^-$ ions: Excitation energies and state-selective rate coefficients

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Main Authors: Gatchell, Michael, Paul, Raka, Ji, MingChao, Rosén, Stefan, Thomas, Richard D., Cederquist, Henrik, Schmidt, Henning T., Larson, Åsa, Zettergren, Henning
Format: Preprint
Published: 2024
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author Gatchell, Michael
Paul, Raka
Ji, MingChao
Rosén, Stefan
Thomas, Richard D.
Cederquist, Henrik
Schmidt, Henning T.
Larson, Åsa
Zettergren, Henning
author_facet Gatchell, Michael
Paul, Raka
Ji, MingChao
Rosén, Stefan
Thomas, Richard D.
Cederquist, Henrik
Schmidt, Henning T.
Larson, Åsa
Zettergren, Henning
contents Context: Mutual neutralization between cations and anions play an important role in determining the charge-balance in certain astrophysical environments. However, empirical data for such reactions involving complex molecular species has been lacking due to challenges in performing experimental studies, leaving the astronomical community to rely on decades old models with large uncertainties for describing these processes in the interstellar medium. Aims: To investigate the mutual neutralization (MN) reaction, C$_{60}^+$ + C$_{60}^-$ $\rightarrow$ C$_{60}^*$ + C$_{60}$, for collisions at interstellar-like conditions. Methods: The mutual neutralization reaction between C$_{60}^+$ and C$_{60}^-$ at collision energies of 100\,meV was studied using the Double ElectroStatic Ion Ring ExpEriment, DESIREE, and its merged-beam capabilities. To aid in the interpretation of the experimental results, semi-classical modeling based on the Landau-Zener approach was performed for the studied reaction. Results: We experimentally identify a narrow range of kinetic energies for the neutral reaction products. Modeling was used to calculate the quantum state-selective reaction probabilities, absolute cross sections, and rate coefficients of these MN reactions, using the experimental results as a benchmark. The MN cross sections are compared with model results for electron attachment to C$_{60}$ and electron recombination with C$_{60}^+$. Conclusions: The present results show that it is crucial to take mutual polarization effects, the finite sizes, and the final quantum states of both molecular ions into account for reliable predictions of MN rates expected to strongly influence the charge-balance and chemistry in, e.g., dense molecular clouds.
format Preprint
id arxiv_https___arxiv_org_abs_2409_11851
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Mutual neutralization of C$_{60}^+$ and C$_{60}^-$ ions: Excitation energies and state-selective rate coefficients
Gatchell, Michael
Paul, Raka
Ji, MingChao
Rosén, Stefan
Thomas, Richard D.
Cederquist, Henrik
Schmidt, Henning T.
Larson, Åsa
Zettergren, Henning
Astrophysics of Galaxies
Chemical Physics
Context: Mutual neutralization between cations and anions play an important role in determining the charge-balance in certain astrophysical environments. However, empirical data for such reactions involving complex molecular species has been lacking due to challenges in performing experimental studies, leaving the astronomical community to rely on decades old models with large uncertainties for describing these processes in the interstellar medium. Aims: To investigate the mutual neutralization (MN) reaction, C$_{60}^+$ + C$_{60}^-$ $\rightarrow$ C$_{60}^*$ + C$_{60}$, for collisions at interstellar-like conditions. Methods: The mutual neutralization reaction between C$_{60}^+$ and C$_{60}^-$ at collision energies of 100\,meV was studied using the Double ElectroStatic Ion Ring ExpEriment, DESIREE, and its merged-beam capabilities. To aid in the interpretation of the experimental results, semi-classical modeling based on the Landau-Zener approach was performed for the studied reaction. Results: We experimentally identify a narrow range of kinetic energies for the neutral reaction products. Modeling was used to calculate the quantum state-selective reaction probabilities, absolute cross sections, and rate coefficients of these MN reactions, using the experimental results as a benchmark. The MN cross sections are compared with model results for electron attachment to C$_{60}$ and electron recombination with C$_{60}^+$. Conclusions: The present results show that it is crucial to take mutual polarization effects, the finite sizes, and the final quantum states of both molecular ions into account for reliable predictions of MN rates expected to strongly influence the charge-balance and chemistry in, e.g., dense molecular clouds.
title Mutual neutralization of C$_{60}^+$ and C$_{60}^-$ ions: Excitation energies and state-selective rate coefficients
topic Astrophysics of Galaxies
Chemical Physics
url https://arxiv.org/abs/2409.11851